Adaptive light source

ABSTRACT

A method according to embodiments of the invention includes creating a three-dimensional profile of a scene, calculating a relative amount of light for each portion of the scene based on the three-dimensional profile, and activating a light source to provide a first amount of light to a first portion of the scene, and a second amount of light to a second portion of the scene. The first amount and the second amount are different. The first amount and the second amount are determined by calculating a relative amount of light for each portion of the scene.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 17/537,614, filed Nov. 30, 2021, which is a continuation ofU.S. patent application Ser. No. 16/790,433, filed Feb. 13, 2020, whichis a continuation of U.S. patent application Ser. No. 15/773,356, filedMay 3, 2018, which is a § 371 application of International ApplicationNo. PCT/EP2016/076360 filed on Nov. 2, 2016 and titled “ADAPTIVE LIGHTSOURCE,” which claims the benefit of U.S. Provisional Application No.62/253,580 filed on Nov. 10, 2015 and European Patent Application No.16158004.8 filed on Mar. 1, 2016. U.S. patent application Ser. Nos.17/537,614, 16/790,433, 15/773,356, International Application No.PCT/EP2016/076360, U.S. Provisional Application No. 62/253,580, andEuropean Patent Application No. 16158004.8 are incorporated herein.

BACKGROUND

Semiconductor light-emitting devices including light emitting diodes(LEDs), resonant cavity light emitting diodes (RCLEDs), vertical cavitylaser diodes (VCSELs), and edge emitting lasers are among the mostefficient light sources currently available. Material systems currentlyof interest for manufacturing of high-brightness light emitting devicescapable of operation across the visible spectrum include Group III-Vsemiconductors, particularly binary, ternary, and quaternary alloys ofgallium, aluminum, indium, and nitrogen, also referred to as III-nitridematerials. Typically, III-nitride light emitting devices are fabricatedby epitaxially growing a stack of semiconductor layers of differentcompositions and dopant concentrations on a sapphire, silicon carbide,III-nitride, or other suitable substrate by metal-organic chemical vapordeposition (MOCVD), molecular beam epitaxy (MBE), or other epitaxialtechniques. The stack often includes one or more n-type layers dopedwith, for example, Si, formed over the substrate, one or more lightemitting layers in an active region formed over the n-type layer orlayers, and one or more p-type layers doped with, for example, Mg,formed over the active region. Electrical contacts are formed on the n-and p-type regions.

Due to their compact size and low power requirements, semiconductorlight-emitting devices are attractive candidates for light sources suchas camera flashes for hand-held, battery-powered devices, such ascameras and cell phones.

SUMMARY

According to embodiments of the invention, a light source is providedwhich may be used, for example, as a flash for a camera, or for anyother suitable use. The light source is configured such that theillumination pattern emitted by the light source may be altered. Forexample, when used as a camera flash, for a given scene in the field ofview of the camera, the light source may provide more light to parts ofthe scene that are not well lit by ambient light, and less light toparts of the scene that are well lit by ambient light.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a system including at least onesemiconductor light-emitting device as a light source.

FIGS. 2A, 2B, and 2C illustrate methods of illuminating a scene using,for example, the system of FIG. 1 .

FIG. 3 illustrates a scene to be illuminated.

FIG. 4 illustrates a three dimensional (3D) map of the scene illustratedin FIG. 3 .

FIG. 5 illustrates a flash intensity profile for the scene illustratedin FIG. 3 .

FIG. 6 is a cross sectional view of one example of a light source.

FIG. 7 is a top view of an array of LEDs.

FIG. 8 is a cross sectional view of one LED in the array of FIG. 7 .

FIG. 9 illustrates the scene that is illuminated in the examples in thefollowing figures.

FIGS. 10A, 11A, 12A, 13A, 14A, and 15A illustrate different illuminanceprofiles for the scene illustrated in FIG. 9 .

FIGS. 10B, 11B, 12B, 13B, 14B, and 15B illustrate the amount of currentapplied to the LEDs in the array of FIG. 7 to generate the illuminanceprofiles illustrated in FIGS. 10A, 11A, 12A, 13A, 14A, and 15A.

FIGS. 16 and 17B illustrate the amount of current applied to the LEDs inthe array of FIG. 7 to generate illuminance profiles for a zoomingapplication.

FIG. 17A illustrates how the scene is illuminated when the LEDs aresupplied with varying levels of current as illustrated in FIG. 17B.

FIG. 18A illustrates how the scene is illuminated when the LEDs aresupplied with varying levels of current as illustrated in FIG. 18B.

FIG. 18B illustrates the amount of current applied to the LEDs in thearray of FIG. 7 to generate an illuminance profile for a wide-angleapplication.

FIG. 19 is a cross sectional view of an array of LEDs with individualoptics.

FIG. 20 illustrates a light source with multiple LED arrays.

FIG. 21 illustrates a scanning, narrow-beam light source.

FIG. 22 illustrates a light source with a matrix control element.

FIG. 23 illustrates a light source with light emitters that emit lightof different colors or color temperatures.

DETAILED DESCRIPTION

Though in the description below, embodiments of the invention aredescribed as camera flashes, other uses are contemplated and are withinthe scope of the invention.

One problem with all camera flashes is that objects close to the cameraare often overexposed while objects further from the camera do not getenough light. Embodiments of the invention include a light source suchas a camera flash, for example for a portable or battery-powered device,or for a larger non-battery-powered photo studio flash. Light sourcesaccording to embodiments of the invention may adapt their illuminanceprofiles to the scene and deliver the right amount of light to allobjects on the scene. The adaptive light source according to embodimentsof the invention may include a semiconductor light source such as asemiconductor light-emitting device, thought any suitable light may beused.

FIG. 1 illustrates an example of an adaptive light source, according toembodiments of the invention. The system illustrated in FIG. 1 may beincluded in a smart phone or any suitable device. The system illustratedin FIG. 1 includes a light source 10 connected to a driver 12. Thedriver 12 supplies power to the light source 10, as described below. Thedriver 12 is connected to a microprocessor 14. The microprocessorreceives input from an input device 18 and camera 11. The system mayalso include 3D sensor 16. The input device 18 may be, for example, auser-activated input device such as a button that a user presses to takea picture. The input device 18 may not require a user input in someembodiments, such as in the case where a picture is taken automatically.The input device 18 may be omitted in some embodiments.

The 3D sensor 16 may be any suitable sensor capable of making a 3Dprofile of the scene, prior to taking a picture. In some embodiments, 3Dsensor 16 may be a time of flight (ToF) camera. A ToF camera measuresthe time it takes for light reflected from objects to travel back to theToF camera. The time may be used to calculate the distance to eachobject in the scene. In some embodiments, 3D sensor 16 may be astructured light sensor. A structured light sensor includes a projectiondevice that projects a specially designed pattern of light on the scene.A camera also included in the structured light sensor measures theposition of each part of the light pattern reflected from the objects ofthe scene and determines the distance to these objects by triangulation.In some embodiments, 3D sensor 16 may be an auxiliary camera or cameraspositioned at a distance from each other in the body of the device. Bycomparing the position of the objects as seen by the auxiliary cameras,distances to each object can be determined by triangulation. In someembodiments, 3D sensor 16 is the autofocus signal of the main camera inthe device. While scanning the focus position of the camera lens, thesystem can detect at which positions which parts of the scene are infocus. A 3D profile of the scene is then built by translating thecorresponding lens positions into the distances to the objects that arein focus for these positions. A suitable autofocus signal is derived byconventional methods, for example by measuring the contrast or byutilizing phase detection sensors within the camera sensor. When phasedetection sensors are used, in some embodiments, for optimal functioningof the adaptive flash, the positions of individual phase detectionsensors may correspond to areas illuminated by separate segments of thelight source 10, as described below.

One example of method for using the system illustrated in FIG. 1 isillustrated in FIG. 2A. In block 20 an input is generated, for exampleinstructing that a picture be taken. In block 22 camera 11 takes a firstpreliminary image of the scene (corresponding to the camera's field ofview) with flash turned off. In block 24 light source 10 is turned on inlow light output mode (typically called “torch mode”). At this time theilluminance profile of the light source 10 is kept uniform where“uniform” means all portions of the scene are illuminated with a knownillumination profile. In block 26 a second preliminary image is capturedwhile light source 10 continues to be on with uniform illuminanceprofile and low brightness. In block 27 the system calculates theoptimum brightness for all parts of the scene to achieve optimalexposure. This can be done by subtracting the pixel brightness values offirst preliminary image from the respective pixel brightness values ofsecond image, and scaling the differences to achieve the optimalexposure levels. In block 28 the final picture is taken by camera 11with the light source 10 activated according to the illuminance profilecalculated in block 27.

Another example of method for using the system illustrated in FIG. 1 isillustrated in FIG. 2B. In block 200, an input is generated, for exampleinstructing that a picture be taken. In block 220 camera 11 takes afirst preliminary image of the scene (corresponding to the camera'sfield of view) with flash turned off. In block 230, a 3D profile of thescene is generated. For example, 3D sensor 16 may generate the 3Dprofile of the scene, or 3D sensor 16 may sense data about the scene andtransmit the data to microprocessor 14, which may generate the 3Dprofile of the scene. In block 270 the system calculates the optimumbrightness for all parts of the scene to achieve optimal exposure. Inblock 280, based on the calculation performed in block 270, the scene isilluminated by the light source.

Another example of method for using the system illustrated in FIG. 1 isshown in FIG. 2C. In block 2000 an input is generated, for exampleinstructing that a picture be taken. In block 2200 camera 11 takes afirst preliminary image of the scene (corresponding to the camera'sfield of view) with flash turned off. In block 2300, a 3D profile of thescene is generated. In block 2400, light source 10 is turned on in lowlight output mode (typically called “torch mode”). At this time theilluminance profile of the light source 10 is kept uniform where“uniform” means all portions of the scenes are illuminated. In block2600 a second preliminary image is captured with light source 10 intorch mode. In block 2700 the system calculates the optimum brightnessfor all parts of the scene to achieve optimal exposure based on theinput of the 2 images taken and the 3D profile as described above in thetext accompanying FIG. 2A and FIG. 2B. In block 2800 the final pictureis taken by camera 11 with the light source 10 activated according tothe illuminance profile calculated in block 2700.

In each of FIGS. 2A, 2B, and 2C, the input may be, for example, a userinput such as the user pushing a button, an input generated bymicroprocessor 14 (for example, if microprocessor 14 is programmed totake a picture at a predetermined time, or at a predetermined interval),or any other suitable input. FIG. 3 illustrates a scene to be capturedin a picture when the input is generated. The scene illustrated in FIG.3 includes a first person 30 in the foreground, and a second person 32in the background. This scene is selected for illustration purposesonly. Other scenes with multiple objects or persons at various distancesfrom the camera are also suitable for use of the present invention.

FIG. 4 illustrates the 3D profile for the scene illustrated in FIG. 3 .In FIG. 4 , the lighter shades correspond to shorter distance from thecamera, darker shades correspond to larger distance from the camera.Accordingly, the person 30 in the foreground has the lightest shading,indicating the person 30 is closest to the camera. The person 32 in thebackground has darker shading, indicating the person 32 is further fromthe camera. The background is black, indicating the furthest distancefrom the camera

Objects located far from the flash may receive higher light intensity;objects located closer to the flash may receive less light. As iswell-known, illuminance of light decreases according to the inversesquare law of distance (Illuminance˜1/distance²). With the 3D profile ofthe scene the required amount of light to distribute to which portionsof the scene can therefore be calculated. The algorithm calculating therequired intensity profile may also take into account the illuminancethat each of the objects in the scene receives from ambient light,information gathered with the capture of a 1^(st) image, and may adjustthe amount of flash light accordingly. For example, objects 30 that arealready well-illuminated, for example because they are lightly coloredor reflective, may receive less light; objects that are notwell-illuminated, for example because they are dark or not reflective,may receive more light than may be calculated solely based on theirdistance from the light source, as determined by the 3D profile.

Digital cameras and their image processors typically include facerecognition algorithms. In some embodiments, information from a facerecognition algorithm may be used to better illuminate faces compared toother objects. If there is not enough light to expose the completepicture well, faces benefit from more light. If the person is too closeand there is a danger of overexposure, this feature should be turnedoff, such that more light is not directed to the face. In someembodiments, the calculation of relative light from the 3D profile mayreduce the amount of light sent towards the eyes of the person tominimize “red eye” in the picture.

In some embodiments, the calculation of relative light from the 3Dprofile may identify parts of the scene that are very far from the flashand cannot be properly illuminated. A minimal amount of light is sent tothese parts of the scene, in order to maximize the amount of light senttowards the useful parts of the scene and thus provide better use ofavailable drive current capability.

In some embodiments, a user interface (for example, the touch screen ona smart phone) may allow a user control over the relative amount oflight sent to each portion of the scene. For example, the user may turnadaptive features of the flash on and off, may turn various parts of thealgorithm used to calculate the relative light from the 3D profile(described above) on and off, and may manually create flash accents onthe scene.

Several illumination modes are contemplated by embodiments of theinvention.

In some embodiments, in a first group of illumination modes,illumination from light source 10 is distributed across the scene toachieve the most homogenously useful illuminated picture. In particular,in some embodiments, overexposure is minimized: in the case whereforeground is well illuminated by ambient light, all light from lightsource 10 is directed to the background. In some embodiments, the lightsource acts as a fill in flash: in the case where the background is wellilluminated by ambient light, all light from light source 10 is directedto foreground. In some embodiments, when the foreground and thebackground are evenly illuminated by ambient lighting, light from lightsource 10 may be send mostly to the background. In some embodiments, inthe case of a dark foreground, light from light source 10 illuminatesthe foreground just enough for a good picture, and the rest of the lightfrom light source 10 is sent to the background.

In some embodiments, in a second group of illumination modes, selectedobjects are illuminated. In particular, in some embodiments, incombination with face recognition, faces may be weighted highest forbest illumination. In some embodiments, in combination with facerecognition, background around faces (or other objects) may receive lesslight, for example to increase contrast between the illuminated face andthe background nearest the face. In some embodiments, selected zones ofthe scene are identified for example by a user input. Light from lightsource 10 may be directed only within the selected zone. Examples ofselected zones include zoomed-in images, or otherwise-identifiedportions of the scene. In some embodiments, for pictures of, forexample, business cards, light from light source 10 may be emitted witha very high uniformity level.

FIG. 5 illustrates light provided to the scene of FIG. 3 based on thecalculation illustrated in FIG. 4 . In FIG. 5 , lighter shadingcorresponds to more light from light source 10, and darker shadingcorresponds to less light from light source 10. As illustrated in FIG. 5, more light is provided in region 42, corresponding to the backgroundperson 32, while less light is provided in region 40, corresponding toforeground person 30. Extra light is provided to the face 52 of theperson in the background. The least amount of light may be provided tothe background where neither person 30 nor person 32 appears (notshown).

FIGS. 6, 7, and 8 illustrate one example of a light source 10, which maybe used in the system illustrated in FIG. 1 . Any suitable light sourcemay be used and embodiments of the invention are not limited to thestructures illustrated in FIGS. 6, 7, and 8 .

FIG. 7 is a top view of a square array 60 of LEDs 62. The LEDs 62 may bemonolithically grown on a single substrate. Alternatively, the LEDs 62need not be monolithically grown on a single substrate, but may be dicedthen arranged on a mount such that neighboring LEDs are very closetogether. In some embodiments, the gap between LEDs 62 is less than ⅓ ofa dimension (for example, the width) of an individual LED 62. Though a3×3 square array is illustrated, any suitable number of LEDs may beused, and the array need not be square, it may be rectangular or anysuitable shape. The size of individual LEDs may depend on several designparameters as, for example, building volume with optical lens included,field of view of the camera and number of LEDs in the array. Forexample, the array must include enough LEDs to illuminate the totalfield of view of the camera (i.e. the entire scene). For smart phoneapplications, the total width of the array may be no more than 2 mm insome embodiments. For larger cameras, the width of the array may be nomore than 10 mm in some embodiments. Though the individual LEDs aresquare, this is not required; rectangular LEDs or LEDs of any suitableshape may be used.

FIG. 6 is a cross sectional view of the light source 10. The array 60 ofLEDs 62 is positioned such that a majority of light extracted from thearray 60 is emitted toward an optic 64. In the example illustrated,optic 64 is spaced apart from the array 60. Alternatively, the optic 64may be placed on top of array 60. Optic 64 may be any suitable structurethat collimates the light and directs light to the appropriate area ofthe scene. Optic 64 may be, for example, a lens, multiple lenses, one ormore Fresnel lenses, one or more refractive lens, one or more totalinternal reflection lens elements, one or more reflectors, one or morecollimators, or any other suitable optic. In the examples below, optic64 is a Fresnel lens. The light source may be in the shape of a box 66,with the array 60 disposed on a bottom of the box, and the optic 64forming the top of the box. Interior sidewalls 68 of the box, anyportion of the bottom that is not occupied by the array 60, and anyportion of the top that is not occupied by the optic 64, are part of theoptical design, and therefore may be reflective or light absorbing asappropriate.

FIG. 8 is a cross sectional view of one example of a single LED 62 inthe array illustrated in FIGS. 6 and 7 . Any suitable LED may be usedand embodiments of the invention are not limited to the structureillustrated in FIG. 8 . In the device of FIG. 8 , a majority of light isextracted from the LED through the growth substrate. Such a device maybe referred to as a flip chip device. The LED of FIG. 8 is formed bygrowing a III-nitride semiconductor structure on a growth substrate 70as is known in the art. The growth substrate is often sapphire but maybe any suitable substrate such as, for example, a non-III-nitridematerial, SiC, Si, GaN, or a composite substrate. A surface of thegrowth substrate on which the III-nitride semiconductor structure isgrown may be patterned, roughened, or textured before growth, which mayimprove light extraction from the device. A surface of the growthsubstrate opposite the growth surface (i.e. the surface through which amajority of light is extracted in a flip chip configuration) may bepatterned, roughened or textured before or after growth, which mayimprove light extraction from the device.

The semiconductor structure includes a light emitting or active regionsandwiched between n- and p-type regions. An n-type region 72 may begrown first and may include multiple layers of different compositionsand dopant concentration including, for example, preparation layers suchas buffer layers or nucleation layers, which may be n-type or notintentionally doped, and n- or even p-type device layers designed forparticular optical, material, or electrical properties desirable for thelight emitting region to efficiently emit light. A light emitting oractive region 74 is grown over the n-type region. Examples of suitablelight emitting regions include a single thick or thin light emittinglayer, or a multiple quantum well light emitting region includingmultiple thin or thick light emitting layers separated by barrierlayers. A p-type region 76 may then be grown over the light emittingregion. Like the n-type region, the p-type region may include multiplelayers of different composition, thickness, and dopant concentration,including layers that are not intentionally doped, or n-type layers.

After growth of the semiconductor structure, a reflective p-contact 78is formed on the surface of the p-type region. The p-contact 78 oftenincludes multiple conductive layers such as a reflective metal and aguard metal which may prevent or reduce electromigration of thereflective metal. The reflective metal is often silver but any suitablematerial or materials may be used. After forming the p-contact 78, aportion of the p-contact 78, the p-type region 76, and the active region74 is removed to expose a portion of the n-type region 72 on which ann-contact 80 is formed. The n- and p-contacts 80 and 78 are electricallyisolated from each other by a gap 82 which may be filled with adielectric such as an oxide of silicon or any other suitable material.Multiple n-contact vias may be formed; the n- and p-contacts 80 and 78are not limited to the arrangement illustrated in FIG. 8 . The n- andp-contacts may be redistributed to form bond pads with adielectric/metal stack, as is known in the art (not shown).

As described above, the LEDs 62 in the array 60 may be formed on asingle wafer, then diced from the wafer as an array 60 with individualLEDs 62 in the array still attached to a single growth substrateportion. Alternatively, many LEDs 62 may be formed on a single wafer,then diced from the wafer, such that already-diced, individual LEDs aredisposed on a mount to form array 60.

The substrate 70 may be thinned after growth of the semiconductorstructure or after forming the individual devices. In some embodiments,the substrate is removed from the device of FIG. 8 . A majority of lightextracted from the device of FIG. 8 is extracted through the substrate70 (or the surface of the semiconductor structure exposed by removingthe substrate 70). Embodiments of the invention are not limited to flipchip LEDs—any suitable device may be used.

A wavelength converting structure 84 may be disposed in the path oflight extracted from the light emitting device. The wavelengthconverting structure includes one or more wavelength convertingmaterials which may be, for example, conventional phosphors, organicphosphors, quantum dots, organic semiconductors, II-VI or III-Vsemiconductors, II-VI or III-V semiconductor quantum dots ornanocrystals, dyes, polymers, or other materials that luminesce. Thewavelength converting material absorbs light emitted by the LED andemits light of one or more different wavelengths. Unconverted lightemitted by the LED is often part of the final spectrum of lightextracted from the structure, though it need not be. The final spectrumof light extracted from the structure may be white, polychromatic, ormonochromatic. Examples of common combinations include a blue-emittingLED combined with a yellow-emitting wavelength converting material, ablue-emitting LED combined with green- and red-emitting wavelengthconverting materials, a UV-emitting LED combined with blue- andyellow-emitting wavelength converting materials, and a UV-emitting LEDcombined with blue-, green-, and red-emitting wavelength convertingmaterials. Wavelength converting materials emitting other colors oflight may be added to tailor the spectrum of light extracted from thestructure. The wavelength converting structure 84 may include lightscattering or light diffusing elements such as TiO₂.

In some embodiments, the wavelength converting structure 84 is astructure that is fabricated separately from the LED and attached to theLED, for example through wafer bonding or a suitable adhesive such assilicone or epoxy. One example of such a pre-fabricated wavelengthconverting element is a ceramic phosphor, which is formed by, forexample, sintering powder phosphor or the precursor materials ofphosphor into a ceramic slab, which may then be diced into individualwavelength converting elements. A ceramic phosphor may also be formedby, for example tape casting, where the ceramic is fabricated to thecorrect shape, with no dicing or cutting necessary. Examples of suitablenon-ceramic pre-formed wavelength converting elements include powderphosphors that are dispersed in transparent material such as silicone orglass that is rolled, cast, or otherwise formed into a sheet, thensingulated into individual wavelength converting elements, powderphosphors that are disposed in a transparent material such as siliconeand laminated over the wafer of LEDs or individual LEDs, and phosphormixed with silicone and disposed on a transparent substrate. Thewavelength converting element need not be pre-formed, it may be, forexample, wavelength converting material mixed with transparent binderthat is laminated, dispensed, deposited, screen-printed,electrophoretically deposited, or otherwise positioned in the path oflight emitted by the LEDs.

The wavelength converting structure 84 need not be disposed in directcontact with the LEDs as illustrated in FIG. 8 ; in some embodiments,the wavelength converting structure 84 is spaced apart from the LEDs.

The wavelength converting structure 84 may be a monolithic elementcovering multiple or all LEDs in an array, or may be structured intoseparate segments, each attached to a corresponding LED. Gaps betweenthese separate segments of the wavelength conversion structure 84 may befilled with optically reflective material to confine light emission fromeach segment to this segment only.

Interconnects (not shown) such as, for example, solder, stud bumps, goldlayers, or any other suitable structure, may be used to electrically andphysically connect the LEDs 62 in the array 60 to a structure such as amount, a printed circuit board, or any other suitable structure. Themount may be configured such that individual LEDs 62 may be individuallycontrolled by driver 12 of FIG. 1 . The light emitted by the individualLEDs 62 illuminates a different part of the scene. By changing thecurrent to individual LEDs, the light provided to a corresponding partof the scene can be modified. The optimal illuminance profile for thescene, calculated as described above, may be obtained by providing anappropriate level of current to each LED 62.

In some devices such as mobile or battery-powered devices, the maximumamount of current available for the adaptive light source of FIG. 1 isoften limited by the capabilities of the device battery. When definingthe drive current levels to all the LEDs 62, the system typically takesinto account the maximum available current budget, and thereby definesthe drive current level for each LED 62 such that the total drivecurrent does not exceed the maximum, while the correct ratio ofintensity between the LEDs is maintained and total light output ismaximized.

FIG. 9 illustrates a scene to be illuminated in the examples illustratedbelow in FIGS. 10A, 11A, 12A, 13A, 14A, and 15A. The amount of currentprovided to each LED for each example is illustrated in FIGS. 10B, 11B,12B, 13B, 14B, and 15B. The target 88, identified by the dashed line inFIG. 9 , requires more light than the rest of the scene, according tothe calculation from the 3D profile, described above. In each of FIGS.10A, 11A, 12A, 13A, 14A, and 15A, the amount of light provided to aregion decreases with increasing darkness of the shading. The lightdistributions illustrated in each figure may be relative.

FIG. 10A illustrates how the scene is illuminated when all LEDs 62 aresupplied with the same amount of current, as illustrated in FIG. 10B.The center of the scene is brightly illuminated, while the outer edgesof the scene are less illuminated. Accordingly, the portion of thetarget near the center of the scene is more illuminated than the portionof the target near the edge of the scene.

FIG. 11A illustrates how the scene is illuminated when only three LEDsare supplied with current, each of the three receiving the same amountof current, while the other six LEDs receive no current. The three LEDs91, 92, and 93 supplied with current are the center LED, and the twobottom LEDs in the left-most column, as illustrated in FIG. 11B. Asillustrated in FIG. 11A, the right side of the scene, correspondingroughly to the target, is more brightly illuminated than the rest of thescene. The current density for LEDs 91, 92, and 93 in FIG. 11B may bethree times higher than the case illustrated in FIG. 10B, where all LEDsare supplied with equal current. The illuminance of the target in FIG.11A is about 1.6 times higher than the illuminance of the target in FIG.10A.

To obtain higher illuminance, fewer segments can be switched on, asillustrated in two examples shown in FIGS. 12A, 12B, 13A, and 13B.

FIG. 12A illustrates how the scene is illuminated when only two LEDs aresupplied with current, each receiving the same amount of current, whilethe other seven LEDs receive no current. The two LEDs 94 and 95 suppliedwith current are the two bottom LEDs in the left-most column, asillustrated in FIG. 12B. As illustrated in FIG. 12A, the right side ofthe scene, corresponding roughly to the target, is more brightlyilluminated than the rest of the scene. The illuminance of the target inFIG. 12A is greater than the illuminance of the target in FIG. 11A.

FIG. 13A illustrates how the scene is illuminated when only a single LEDis supplied with current while the other eight LEDs receive no current.The LED 96 supplied with current is the center LED in the left-mostcolumn, as illustrated in FIG. 13B. As illustrated in FIG. 13A, theright side of the scene, corresponding roughly to the target, is morebrightly illuminated than the rest of the scene, though the highlyilluminated spot is smaller than in FIGS. 12A and 11A. The illuminanceof the target in FIG. 13A is greater than the illuminance of the targetin FIG. 11A.

To improve the uniformity of illuminance across the entire target, thecurrent supplied to different LEDs may be varied, as illustrated in twoexamples shown in FIGS. 14A, 14B, 15A, and 15B.

FIG. 14A illustrates how the scene is illuminated when six LEDs aresupplied with varying levels of current and three LEDs receive nocurrent. The center LED 96 in the left column is supplied with fivetimes more current than the five LEDs 97, 98, 99, 100, and 101 whichsurround LED 96. The three LEDs in the right column receive no current,as illustrated in FIG. 14B. As illustrated in FIG. 14A, the right sideof the scene, corresponding roughly to the target, is more brightlyilluminated than the rest of the scene. The illuminance of the target ismore uniform than in, for example, FIG. 13A.

FIG. 15A illustrates how the scene is illuminated when four LEDs aresupplied with varying levels of current and five LEDs receive nocurrent. The center LED 102 in the left column is supplied with fourtimes more current than the bottom LED 105 in the center column, andwith twice as much current as the center LED 104 and the bottom LED 103in the left column. The top row of LEDs and the LEDs in the right columnreceive no current, as illustrated in FIG. 15B. As illustrated in FIG.15A, the right side of the scene, corresponding roughly to the target,is more brightly illuminated than the rest of the scene. The illuminanceof the target is more uniform than in, for example, FIG. 13A.

FIGS. 16, 17B, and 18B illustrate how current may be applied to thearray 60 of LEDs 62 in FIG. 6 , for zoom and wide angle applications.When a command to zoom in the camera lens is received, LEDs near thecenter of the array receive more current, as illustrated in FIGS. 16 and17B. FIG. 17A illustrates how the scene is illuminated when the LEDs aresupplied with varying levels of current as illustrated in FIG. 17B.

When a command to zoom out the camera lens is received, LEDs near theedge of the array receive more current, as illustrated in FIG. 18B. FIG.18A illustrates how the scene is illuminated when the LEDs are suppliedwith varying levels of current as illustrated in FIG. 18B.

In FIG. 16 , for a zoom application, just the center LED 110 is suppliedwith current, while the eight LEDs surrounding the center LED receive nocurrent. The center of the scene will be brightly illuminated, while theedges of the scene will receive less light. Illuminance at the center ofthe scene may be increased by 2.2 times over the center of the scene inFIG. 10A, where all nine LEDs receive equal current.

In FIG. 17B, for a zoom application, the center LED 111 is supplied withtwice as much current as LEDs 112, and four times as much current asLEDs 114. The center of the scene is more illuminated than the edges ofthe scene. Illuminance at the center of the scene may be increased by1.15 times over the center of the scene in FIG. 10A, where all nine LEDsreceive equal current.

In FIG. 18B, for a wide-angle application, the eight LEDs 118 at theedges of the array receive equal current, while the center LED 116receives no current. Illuminance at the center of the scene may bereduced to 0.85 times the illuminance at the center of the scene in FIG.10A, where all nine LEDs receive equal current.

The adaptive light source may be used to illuminate multiple targets, byproviding current to only the LEDs corresponding to each target, or byproviding more current to the LEDs corresponding to each target. Theadaptive flash may be used to reduce overexposure in a scene containingelements that are close to the camera and far from the camera, byproviding current to only the LEDs corresponding to the elements farfrom the camera, or by providing more current to the LEDs correspondingto the elements far from the camera.

The illuminance values given for the examples above are calculated forthe illustrated 3×3 array with a single Fresnel lens. The light outputof each LED in the examples above can be controlled by the drivercurrent of the LED, or by pulse duration with a fixed current.

FIGS. 19, 20, 21, 22, and 23 illustrate alternative light sources.

In the light source of FIG. 19 , each LED 62 in the array has anindividual optic 122, rather than a single optic for the entire array,as illustrated in FIG. 6 . Each optic 122 directs light from its LED toa specific portion of the scene. Optics 122 may be any suitable opticincluding, for example, lenses, dome lenses, Fresnel lenses, reflectors,total internal reflection lenses, or any other suitable structure.Optics 122 need not be identical; different optics may be used fordifferent LEDs 62 in the array.

The light source of FIG. 20 includes multiple LED arrays with multipleoptical elements. For example, FIG. 20 illustrates two 3×3 arrays, eachwith a single corresponding Fresnel lens. More or fewer arrays may beused, and the arrays are not limited to the device illustrated. In someembodiments, each array illuminates a part of the scene. Array 124 inFIG. 20 illuminates the top 128 of the scene, while array 126illuminates the bottom 130 of the scene. In some embodiments, the arraysilluminate overlapping parts of the scene, in order to provide morelight to the overlapping parts. For example, the arrays may overlap inthe center of the scene, which may be a part of the scene that oftenrequires more light than the edges. The light source of FIG. 21 uses anarrow-beam light emitting device such as, for example, a laser. Thelight source of FIG. 21 includes a laser 140 with a wavelengthconverting element 142 disposed in the path of the light from the laser.Focusing optics 144 may create a light beam of the desired size. Thebeam is incident on a first scanning mirror 146, and a second scanningmirror 148, before being incident on the scene 150. The scanning mirrorsmay be moved such that the light beam scans the entire scene, while thedriver controls the intensity of the light source, such that differentparts of the scene may receive different amounts of light. When the beamscans parts of the scene requiring higher intensity, the currentsupplied to the laser increases; when the beam scans parts of the scenerequiring lower intensity, the current supplied to the laser decreases.

The light source of FIG. 22 includes a matrix control element, such as adigital micromirror switching device or a multi-segment liquid crystaldisplay. Light from an LED or laser 152 illuminates the matrix controlelement 154. The intensity of the reflected or transmitted light ismodified depending on the calculated illuminance profile. The reflectedor transmitted light from the matrix switching element 154 is projectedonto the scene 156. Matrix switching element 154 may have many smallmirrors as pixels. The orientation of each mirror can be changed to tunethe intensity at each pixel. The orientation of the mirrors may also beused to create brighter regions, by overlapping the beams from differentmirrors.

The light source of FIG. 23 is color tunable. The light source of FIG.23 includes two arrays, 160 and 162, which are arranged to emit beams166 and 168, respectively, which overlap when they illuminate the scene164. Though two arrays like the array illustrated in FIG. 6 areillustrated, other suitable light emitters may be used. The system mayinclude 3 or more arrays with different emission spectra. Arrays 160 and162 emit different colors of light. For example, arrays 160 and 162 mayboth emit white light, though array 160 may emit white light with adifferent color temperature than array 162—i.e., one of array 160 andarray 162 emits warm white light. For example, the array that emits warmwhite light may emit light with a color temperature as low as 1700 K,and the array that emits cool white light may emit light with a colortemperature as high as 10000 K. The difference in color temperaturebetween the two arrays may be at least 1000 K in some embodiments, atleast 2000 K in some embodiments, at least 3000 K in some embodiments,and at least 4000 K in some embodiments. Alternatively, arrays 160 and162 may emit different monochromatic colors of light. The appropriatecurrent supplied to each LED in each array is calculated such that thesum of light from arrays 160 and 162 has the appropriate illuminance andcolor temperature for each portion of the scene. Arrays (or other lightemitters) emitting additional colors or color temperatures of light maybe added.

In some embodiments, LEDs emitting multiple spectra may be combined in asingle, interleaved array, with a single optic as illustrated in FIG. 6or with individual optics as illustrated in FIG. 19 . LEDs of differentcolors may be arranged in groups, each group illuminating a portion ofthe scene, each group including at least one LED of each differentcolor.

The color tunable light source described above may be used to illuminatedifferent parts of the scene with light of different correlated colortemperature (CCT). For example, a color tunable light source may be usedto equalize the CCT of different ambient illuminants. The sections ofthe scene with low CCT ambient light may be illuminated with higher CCTlight, while the sections of the scene with high CCT ambient light maybe illuminated with lower CCT light.

In some embodiments, light source 10 may be used with different cameras.For example, a smart phone may have multiple cameras, or different smartphone models may use different cameras. The cameras may each have aspecific field of view, for which the flash for that camera is tuned(for example, tuned to provide a minimum level of illumination in thecorner of the field of view). Accordingly, for a conventional flash,each camera requires a separate flash that is tuned to that camera'sfield of view. With adaptive light source according to embodiments ofthe invention, a default current distribution for each camera could bedefined and selected when that camera is selected, such that a singlelight source may be used for multiple cameras. The default for eachcamera may be modified according to the scene being photographed, asdescribed in the embodiments above.

Though in the examples above the semiconductor light emitting device areIII-nitride LEDs that emits blue or UV light, semiconductor lightemitting devices besides LEDs such as laser diodes and semiconductorlight emitting devices made from other materials systems such as otherIII-V materials, III-phosphide, III-arsenide, II-VI materials, ZnO, orSi-based materials may be used.

Having described the invention in detail, those skilled in the art willappreciate that, given the present disclosure, modifications may be madeto the invention without departing from the spirit of the inventiveconcept described herein. In particular, different elements fromdifferent examples or embodiments may be combined. It is not intendedthat the scope of the invention be limited to the specific embodimentsillustrated and described.

What is claimed is:
 1. An imaging system, comprising: a camera having afield of view that includes a scene; a light source configured toilluminate the scene, the light source including a collimating lens anda light-emitting diode (LED) array located at a focal plane of thecollimating lens, the LED array including LEDs that are independentlycontrollable and configured to direct light to different portions of thescene; a driver configured to electrically power the light source andindependently control the LEDs in the LED array; a three-dimensional(3D) sensor configured to determine distances from the imaging system tothe respective portions of the scene; and at least one processorconfigured to: determine a set of power values from the determineddistances, the power values increasing with increasing distance to therespective portions of the scene; cause the driver to electrically powerthe light source to illuminate the scene such that the LEDs in the LEDarray are electrically powered based on the determined power values; andcause the camera to capture an image of the scene while the scene isilluminated.
 2. The imaging system of claim 1, wherein the determinedset of power values at least partially compensates for a decrease inpower density with increasing distance away from the light source. 3.The imaging system of claim 1, wherein the LED array includes LEDs thatare monolithically grown on a single substrate.
 4. The imaging system ofclaim 1, further comprising an input device configured to receive inputfrom a user to initiate the determination of the distances, thedetermination of the set of power values, the powering of the lightsource, and the capture of the image.
 5. The imaging system of claim 1,wherein the 3D sensor includes a time-of-flight camera configured tomeasure time durations for light reflected from the respective portionsof the scene to arrive at the time-of-flight camera.
 6. The imagingsystem of claim 1, wherein the 3D sensor includes a structure lightsensor configured to project a specified pattern onto the scene anddetermine positions of objects in the scene via analysis of distortionof the specified pattern from at least one captured image of the scene.7. The imaging system of claim 1, wherein the 3D sensor includes aplurality of cameras configured to capture images of the scene fromdifferent locations and determine positions of objects in the scene viatriangulation from the captured images.
 8. An imaging system,comprising: a camera having a field of view that includes a scene; alight source that, when operative, illuminates the scene, the lightsource including a collimating lens and a light-emitting diode (LED)array located at a focal plane of the collimating lens, the LED arrayincluding LEDs that are independently controllable and, when operative,direct light to different portions of the scene; a driver that, whenoperative, electrically powers the light source and independentlycontrols the LEDs in the LED array; a three-dimensional (3D) sensorthat, when operative, determines distances from the imaging system tothe respective portions of the scene; and at least one processor that,when operative: determines a set of power values from the determineddistances, the power values increasing with increasing distance to therespective portions of the scene; causes the driver to electricallypower the light source to illuminate the scene such that the LEDs in theLED array are electrically powered based on the determined power values;and causes the camera to capture an image of the scene while the sceneis illuminated.
 9. The imaging system of claim 8, wherein the determinedset of power values at least partially compensates for a decrease inpower density with increasing distance away from the light source. 10.The imaging system of claim 8, wherein the LED array includes LEDs thatare monolithically grown on a single substrate.
 11. The imaging systemof claim 8, further comprising an input device that, when operative,receives input from a user to initiate the determination of thedistances, the determination of the set of power values, the powering ofthe light source, and the capture of the image.
 12. The imaging systemof claim 8, wherein the 3D sensor includes a time-of-flight camera that,when operative, measures time durations for light reflected from therespective portions of the scene to arrive at the time-of-flight camera.13. The imaging system of claim 8, wherein the 3D sensor includes astructure light sensor that, when operative, projects a specifiedpattern onto the scene and determine positions of objects in the scenevia analysis of distortion of the specified pattern from at least onecaptured image of the scene.
 14. The imaging system of claim 8, whereinthe 3D sensor includes a plurality of cameras that, when operative,capture images of the scene from different locations and determinepositions of objects in the scene via triangulation from the capturedimages.
 15. An imaging system, comprising: a camera having a field ofview that includes a scene; a camera flash configured to illuminate thescene, the camera flash including a collimating lens and alight-emitting diode (LED) array located at a focal plane of thecollimating lens, the LED array including LEDs that are independentlycontrollable and configured to direct light to different portions of thescene; a driver configured to electrically power the camera flash andindependently control the LEDs in the LED array; a three-dimensional(3D) sensor configured to determine distances from the imaging system tothe respective portions of the scene; and at least one processorconfigured to: determine a set of power values from the determineddistances, the power values increasing with increasing distance to therespective portions of the scene; cause the driver to electrically powerthe camera flash to illuminate the scene such that the LEDs in the LEDarray are electrically powered based on the determined power values; andcause the camera to capture an image of the scene while the scene isilluminated.
 16. The imaging system of claim 15, wherein the determinedset of power values at least partially compensates for a decrease inpower density with increasing distance away from the camera flash. 17.The imaging system of claim 15, wherein the LED array includes LEDs thatare monolithically grown on a single substrate.
 18. The imaging systemof claim 15, wherein the 3D sensor includes a time-of-flight cameraconfigured to measure time durations for light reflected from therespective portions of the scene to arrive at the time-of-flight camera.19. The imaging system of claim 15, wherein the 3D sensor includes astructure light sensor configured to project a specified pattern ontothe scene and determine positions of objects in the scene via analysisof distortion of the specified pattern from at least one captured imageof the scene.
 20. The imaging system of claim 15, wherein the 3D sensorincludes a plurality of cameras configured to capture images of thescene from different locations and determine positions of objects in thescene via triangulation from the captured images.